The invention relates to an integrated circuit (IC) operational amplifier (op-amp) output stage which is capable of driving an output terminal to within a small increment of the power supply rail potentials. This increment is a single transistor saturation voltage (V.sub.SAT). The output stage circuit is designed to operate in class AB bias conditions and is intended to operate under stable conditions when driving a capacitive load. The circuit employs vertically constructed PNP and NPN IC transistors of the kind set forth in U.S. Pat. No. 4,940,671.
The circuit of the invention is intended for driving capacitive loads and to operate at low supply voltages. Rapid settling time, after transient drive, is desirable and output transistor hard saturation is to be avoided while providing relatively large output currents.